U.S. Pat. No. 4,040,814 issued to R. F. Merkert on Aug. 9, 1977, discloses and claims a method for producing a material containing vanadium and nitrogen substantially in the form of V.sub.2 N in which a mixture of V.sub.2 O.sub.3 and carbon in substantially stoichiometric porportions according to the formula V.sub.2 O.sub.3 +3C.fwdarw.2V+3CO is is placed in a vacuum furnace and subjected to a temperature in a range of from about 1100.degree. C. to 1500.degree. C. under a reduced pressure in the range from about 5 mm to 100 microns. The mixture constituents react under these conditions and evolve CO. The temperature and pressure in the furnace are maintained in the above ranges until CO is essentially no longer evolved from the mixture. Thereafter, nitrogen gas is introduced into the furnace to provide a nitrogen environment in the furnace, preferably at about atmospheric pressure, while the temperature in the furnace is maintained in the range of from about 1100.degree. C. to 1500.degree. C. The nitrogen reacts with the vanadium constituent in the mixture to provide from about 5 to 8% by weight nitrogen. The process is repeated by evacuating the furnace to provide a pressure of from about 5 mm to 100 microns, whereupon additional CO is evolved. Nitrogen gas is again introduced into the furnace to provide a nitrogen environment at about atmospheric pressure and nitrogen further reacts with vanadium constituent in the mixture to provide a further increase of from about 1 to 3% by weight of nitrogen. The process may be repeated one or more times until the nitrogen content of the mixture is in the range of about 10 to 12% by weight.
The aforedescribed method unfortunately suffers from the limitation in that it consumes a significant amount of power due to the intermittent vacuum and nitriting steps. In addition, the total furnace cycle time is too long. The reaction between the mixture constituents, i.e., V.sub.2 O.sub.3 and carbon, is exothermic but so far there has been no attempt to utilize this reaction and reduce cycle time.
It is therefore an object of the present invention to provide an improved method for producing a vanadium- and nitrogen-containing material for use as an addition to steel.
Another more specific object of the present invention is to provide such an improved method which utilizes the energy released by the exothermic reaction between the mixture constituents to reduce power consumption and shorten furnace cycle time.
It has been discovered that the foregoing objects and advantages of the present invention can be achieved by continuously flowing nitrogen gas in the furnace while simultaneously maintaining the temperature and vacuum.